1. Field of the Invention
The present invention relates to a dry process silver salt photosensitive material on which development is carried out by a dry process. It also relates to an image forming method making use of this dry process silver salt photosensitive material.
2. Related Background Art
Silver salt photography making use of silver halides is a recording technique that can achieve excellent photosensitivity and gradation and has been widely used. This photography, however, after imagewise exposure, makes use of a wet process in the processing steps such as developing, fixing and washing, and hence has inferior operability, simplicity and safety, which have hitherto come into question.
As countermeasures therefor, dry-process photographic materials that do not require such wet processing are disclosed in Japanese Patent Publications No. 43-4921, No. 43-4924, etc. These make use of a photosensitive silver halide approximately in an amount required as a catalyst and also a non-photosensitive organic silver salt as an image forming agent. The mechanism by which the organic silver salt acts as an image forming agent is presumed as follows: (1) A silver nucleus is produced from a photosensitive silver halide as a result of imagewise exposure, and it forms a latent image. (2) The silver nucleus serves as a catalyst, an organic silver salt and a reducing agent cause oxidation-reduction reaction upon heating, and the organic silver salt is reduced to metallic silver, which forms a visible image.
As an example of methods of utilizing such a dry process silver salt photosensitive material, Japanese Patent Application Laid-open No. 55-50246 discloses a method of use as a mask. In this method, a silver image is used as a mask. Such conventional dry process silver salt photosensitive materials, however, have been disadvantageous in that they have a narrow latitude for developing temperatures, and silver images formed are reddish, can not be pure-black and also have a low optical density.
The dry process silver salt photosensitive materials are advantageous over wet process silver salt photosensitive materials in view of the fact that no wet processing is required. Accordingly, it has been hitherto sought to make the contrast of the former materials comparable to, or more improved than, that of the latter wet process silver salt photosensitive materials. However, conventional dry process silver salt photosensitive materials have had the problem that they have a narrow latitude for heat development and variations in development performance are caused by delicate differences of heating temperatures.